There are three main types of power supplies: standalone units (like the “bricks” that plug into walls for laptops), built-in units (like in refrigerators, microwaves, and TVs), and hybrid units (like the built-in, yet self-contained power supplies used in desktop computers). Each device needs a different amount of power, or DC, to function. The main task of a power supply is to regulate the voltage so the device is not overheating and is operating properly.